If I got laid off past, how should I tell the interviewer why I

I got an interview for a company from which I was laid off 4 years ago. Actually I had a few interviews from the same company. During the interview, the interviewers always ask me why I left the company last time, I told them the truth that I got laid off. If I don't tell them the truth, they still can find out the reason from HR record. My previous manager wrote very bad words about me. But this is very good opportunity to find a good job. Can everyone give me some suggestions how should I answer this kind of questions? Thank you in advance.